On 9/5/2015 12:05 PM, rattus wrote: > Got it. Sounds like a DAMHIK situation; -) > > So you're saying that VDD_3V3B does not come up quickly enough to power > external devices before the boot configuration is read from the pins? You'd > think we should have held off boot a little longer until supplies settle. > Given there's no P8/9 accessible way to prolong boot, short of driving a > tiny solenoid to hold the reset button down a little longer, how might one > isolate the input protection diodes until bot is safely started?
<snip> > My loadings are a single LVC gate on each line, so basically nothing there. You can use parts specified and designed for hot-plug, which will not load the bus until the supplies stabilize. Alternately, you can use some of the FET isolation/voltage-translation parts (also commonly used to make designs hot-plug safe) which will also not conduct until the power rail is active. See page 9-10 for some details: http://www.ti.com/lit/pdf/scdd001 ...and the rest of the book for lots of part info. and other application details. Or you could just run your buffers off 5V (with TTL level inputs, like an HCT series part) and not have to worry about loading the boot pins before the 3.3V rail comes up. But I don't know what you're driving, so that may not be an option. -- Charles Steinkuehler [email protected] -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
